Environmental and energy related policies, regulations, legislation, and treaties continue to address carbon emissions. As carbon emissions continue to become more frequently monitored, carbon capture and sequestration is likely to be an element of any future greenhouse gas compliance plan.
Natural gas and integrated gasification combined cycle systems (also known as IGCC systems) separate CO2 at atmospheric or slightly elevated pressures. The separated CO2 can then be compressed and captured as high pressurized CO2 that can be used for enhanced oil recovery by deep oil injection. Additional sources of CO2 that are substantially devoid of any known detrimental environmental or energy effects are also desirable.
Industrial gas turbines are often capable of alternatively running on liquid and gaseous fuels, e.g., natural gas. These gas turbines have fuel supply systems for both liquid and gas fuels. The gas turbines generally do not burn both gas and liquid fuels at the same time. Rather, when the gas turbine burns liquid fuel, the gas fuel supply is turned off. Similarly, when the gas turbine burns gaseous fuel, the liquid fuel supply is turned off. Fuel transitions occur during the operation of the gas turbine as the fuel supply is switched from liquid fuel to gaseous fuel, and vice versa.
Gas turbines that burn both liquid and gaseous fuel require a fuel purge system to clear the fuel nozzles in the combustors. The liquid fuel supply system is turned off when a gas turbine operates on gaseous fuel. When the liquid fuel system is turned off, the purge system operates to flush out any remaining liquid fuel from the nozzles of the combustor and provide continuous cooling airflow to the nozzles. As shown in FIG. 1, in a known purge system 100, pressurized air from the discharge of a gas turbine compressor or a separate dedicated purge air compressor 103 clears atomizing air passages, liquid fuel nozzles, and water injection nozzles. During liquid fuel operation, an atomizing air compressor 101 further boosts the pressure of purge air for liquid fuel atomization. Similarly, the gas fuel supply system is turned off when a gas turbine operates on liquid fuel. When the gas fuel supply system is turned off, the purge system 100 operates to flush out any remaining gas fuel from the gas fuel nozzles of the combustor and provides continuous cooling airflow to the nozzles.
A purge system, a system including a purge system, and purge method capable of utilizing CO2 would be desirable in the art.